The present invention relates to a video signal access control system, often referred to as a tv or television set-top box. More specifically, it relates to such a system where access to video signals from a remote source is allowed only if the system is in an authorized location. Additionally, access to some video signals is more restricted geographically than access to other video signals.
Set-top integrated receiver decoder (IRD) boxes are now being used to allow persons to directly receive subscription and pay video transmissions from satellites using small outdoor antennas. Decoder boxes may also be used for encoded or scrambled over the air video signals (i.e., broadcast from ground transmitter to customer/viewer without passing through satellite therebetween) or for cable (i.e., wire or optical fiber) video signals. (Since the functions of the set-top boxes can be realized also by components integrated into a television set, video cassette recorder, or other devices, the terms "customer access control" will be used herein for the components at the customer's location that control access.)
The satellite transmissions may be digitally compressed in order to accommodate many programs on a single carrier and multiple carriers on a single satellite. Many of the programs are authorized for distribution and reception only in certain geographic regions, particularly certain countries, where program rights have been obtained for their transmission and reception. Additionally, a set-top box may be authorized only for non-commercial personal use by consumers and not by hotels, theaters or other commercial activities. It is therefore useful for the operators of a video distribution system (whether satellite, over the air, or cable) that their set-top boxes are operable only at authorized locations and that the boxes inhibit authorization of program descrambling of the boxes at unauthorized locations.
Various patents have issued on IRDs. Although customer access controls such as decoders are usually separate from the television receiver (hence the common name set-top box), it should be understood that they could also be integral (in a common housing) with a television receiver, monitor, or video cassette recorder.
The following U.S. Patents, hereby incorporated by reference, only a few of which will be discussed below, are noted relative to access control for video signals or communications signals:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ Teare et al. 5,243,652 Sept. 07, 1993 Daniel et al. 5,224,161 June 29, 1993 Cohen et al. 5,282,249 Jan. 25, 1994 West, Jr. 5,345,504 Sept. 06, 1994 Mason 4,736,422 April 05, 1988 Jeffers et al. 4,739,510 April 19, 1988 Mason 4,802,215 Jan. 31, 1989 Kudelski et al. 5,144,663 Sept. 01, 1992 Leduc et al. 5,208,856 May 04, 1993 Wilson et al. 5,295,188 Mar. 15, 1994 Naccache et al. 5,347,581 Sept. 13, 1994 Diehl et al. 5,373,557 Dec. 13, 1994 ______________________________________
The Teare patent shows use of a global position system (GPS) receiver to authorize release of an encryption key only when a location versus time track corresponds to a proper use. If the key is released, it allows the remote unit to view a scrambled video tape, which tape is at the remote unit. The remote unit is in an airplane which is allowed to show the video tape when it is in a given location or country and its position changes are consistent with the anticipated flight path.
Daniel shows video descrambling using a smart card and a pseudo-random generator.
Cohen discloses video descrambling using a smart card.
West shows cable television access regulated by a jamming signal.
In other developments, the NAVSTAR GPS achieved full initial operating capability in 1993 and provides precisely timed radio frequency signals from twenty-four orbiting satellites. A GPS receiver utilizes the transmission delay time from multiple orbiting satellites to make a determination of the position of the GPS receiver. The receiver must have a clock with good short term accuracy to lock onto and track a code message sent by a GPS satellite and further to make accurate pseudo-range measurements. A time-offset error between the highly accurate atomic standard clock in each satellite and a receiver can be removed by operating on the signal codes sent from four satellites rather than just three. The extra satellite signal permits a mathematical solution for the time offset as well as the ranges between satellites and receiver.
Some GPS receivers presently cost only a few hundred dollars, making them satisfactory for ships, aircraft and other vehicles where position determination is desired. The GPS receiver includes a microprocessor to perform calculations on measured data, special circuitry to calculate correlations, and requires a visual display, packaging, power supply, etc. Some of these items are already in the set-top box for other purposes and other functions can be simplified by performing a portion of the processing at the up-link site and transmitting the results along with commands over the same communication system providing the video, audio and data programming to the IRD's. The complexity of the IRD processing to accommodate the physical position validation can then be reduced to a level where the cost of electronic circuitry to implement these functions is acceptably small.
In the normal operation of a GPS receiver time-of-arrival measurements of code-division multiplexed radio signals from multiple GPS satellites are made by the receiver. These measurements are then converted to pseudo-range measurements using the radio wave propagation velocity. The range measurements are called pseudo-range because of a time bias error introduced by imperfect receiver time synchronization with the satellites' precise timing controlled by atomic clocks. The time bias is treated as an additional variable in the position calculations and one additional pseudo-range measurement is made to provide an additional equation to solve for this additional variable. Although the calculations to be performed are straight forward, a position solution must be iteratively calculated to converge on a solution. Additionally, corrections must be calculated for propagation effects in order to produce accurate position determination as normally required for airplanes, ships, boats, or other vehicles.
The following U.S. Patents, hereby incorporated by reference, show various GPS receivers and/or methods:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ Holmes et al. 4,807,256 Feb. 21, 1989 Allison et al. 5,359,332 Oct. 25, 1994 Gilbert et al. 5,379,045 Jan. 03, 1995 ______________________________________